The present invention relates to an apparatus and method for controlling a voltage source converter.
In recent years, many power converters for converting alternating current to direct current or vice versa have been used. Power converters of this type are also applied to the field of high voltages. In such an application, converter modules each including semiconductor switching devices, for example, are utilized. That is, such converter modules are connected in series. This configuration can withstand high voltages.
In such a configuration, converter modules are connected, for example, in series to constitute legs. In each leg, electrical current is controlled by controlling the operation of each converter module. Thus, power conversion is achieved between the AC terminal and the DC terminal.
Generally, in the field of electric power conversion, plural phases are often treated. Therefore, the joint in each leg is taken as an AC terminal. On the other hand, the DC terminals of the legs are interconnected.
In this configuration, electric power conversion is made between DC and AC terminals while treating plural phases by providing control such that a periodic electric current flows, the current being determined by the reciprocal of the frequency of the AC system to which the AC terminals are connected.
Such a technique is described, for example, in JP-A-2010-233411.